1. Field of the Invention
This invention relates to removal of produced fluids from well bores, and in particular to the removal of multiple phases of fluids from well bores. Embodiments of the invention relates to the removal of natural gas and water from a natural gas-producing well.
2. Description of the Related Art
In the oil and gas production industry, and more specifically in the production of natural gas, water encroachment into the well bore which extends from the gas-producing formation to surface presents significant difficulties in maintaining production output. Where the produced fluid contains only a small proportion of water, the water will typically remain in droplet form and the velocity of the produced gas flowing from the formation into the well bore and up to surface will often be sufficient to entrain the water droplets and carry the droplets to surface.
However, as the proportion of water in the produced fluid increases, the density of the gas\water droplet column in the well bore rises. The resulting increase in hydrostatic pressure reduces the pressure gradient between the gas-producing formation and the section of well bore which intersects the formation, which may eventually kill the well.
Furthermore, the point may also be reached where the level of water production increases, or the gas velocity decreases, to a point where the velocity of the gas is not sufficient to carry the water droplets out of the well.
One temporary solution to such problems is to install velocity strings in the well bore to restrict the flow area and thus increase the velocity of the produced gas as it travels up the well. However, such velocity strings create significant flow restrictions in the well bore, thus reducing production rates. Also, the point will be reached where the velocity of the gas within the restricted area strings drops below the rate necessary to carry the water droplets to surface, and the well is again killed.
All of these problems are particularly acute in depleted wells; that is, wells which have been producing for some time, and in which the formation pressure has diminished to a level of economic or physical unfeasibility.
To overcome these difficulties it is known to employ artificial lift systems, which may be in the form of compressors or pumps which are located in the well.